A 60-year-old woman whose routine medical checkup revealed thickening of the membrane lining her left lung has become the subject of a rare case report describing Müllerian-type high-grade serous carcinoma that appeared exclusively in the chest, with no detectable primary tumor anywhere in the abdomen or pelvis. The report, published in General Thoracic and Cardiovascular Surgery Cases, documents an exceptionally uncommon presentation of a cancer type that almost always announces itself through abdominopelvic disease, and it illustrates how difficult it can be to classify a malignancy when its usual birthplace yields nothing on imaging, surgical inspection, or microscopic examination.
Müllerian-type high-grade serous carcinoma most commonly originates in the fallopian tube, the ovary, or the peritoneum, and it typically presents with disease concentrated in the abdomen and pelvis. A thoracic presentation without any detectable abdominopelvic primary tumor is described in the report as extremely rare and diagnostically challenging. The authors note that recognizing this pattern matters clinically, because it belongs in the differential diagnosis of malignant pleural effusion and thoracic serous carcinoma of unknown primary in female patients, and because treatment strategies differ substantially between Müllerian-type carcinoma, malignant pleural mesothelioma, and carcinoma of unknown primary.
The patient was referred for evaluation of left pleural thickening found during a routine health check-up, and she reported left-sided back pain that had persisted for one month. Her medical history included hypertension, dyslipidemia, and hyperuricemia, with no significant family history of gynecological malignancy.
Preoperative positron emission tomography using 18F-fluorodeoxyglucose showed increased tracer uptake in the pleural lesion, with a maximum standardized uptake value of 12.5, and found no evidence of intraperitoneal involvement. No cystic lesion was identified on CT. Because no previous CT images obtained before the detection of the pleural lesion were available, the clinical team could not evaluate how the lesion had changed over time, a limitation the authors acknowledge in reconstructing the disease’s course.
To obtain tissue, the surgical team performed a single-port thoracoscopic biopsy with the patient in the right lateral decubitus position, making a 2.5-centimeter skin incision at the anterior axillary line in the seventh intercostal space. Thoracoscopic examination revealed multiple nodules scattered across the parietal pleura and the diaphragmatic surface. A full-thickness biopsy of the parietal pleura was obtained, and pleural effusion was collected for cytological examination, which came back positive for malignant cells.
Immunohistochemical staining showed positivity for PAX8, WT-1, AE1/AE3, CK7, p16, and p53, with p53 overexpression, a pattern supporting an epithelial malignancy of Müllerian type. In contrast, the tumor was negative for calretinin, D2-40, TTF-1, and Napsin A. The authors explain that these findings argued against mesothelial and primary pulmonary tumors, although they caution that calretinin and D2-40 negativity alone does not completely exclude a mesothelial malignancy. TTF-1 and Napsin A negativity argued against a primary pulmonary adenocarcinoma, while p53 overexpression and p16 positivity were compatible with molecular features commonly observed in high-grade serous carcinoma. The pathological findings were reviewed by multiple pathologists, including a gynecological pathologist, and the diagnosis of Müllerian-type high-grade serous carcinoma was made on the basis of the histological and immunohistochemical findings, though no external pathological consultation was performed.
The search for a primary tumor then moved to the abdomen and pelvis. Although the serum CA125 level was elevated at 178.0 U/mL, magnetic resonance imaging showed no intra-abdominal or pelvic primary tumor. Diagnostic and staging laparoscopy with bilateral salpingo-oophorectomy was subsequently performed, with the patient in the lithotomy position under Trendelenburg tilt and a three-port laparoscopic approach established through an open umbilical technique. Mild omental adhesion was observed in the left upper abdomen. The uterus was approximately the size of a hen’s egg, with an intramural myoma at the right uterine horn, but both adnexa had a normal gross appearance. No remarkable findings were seen in the pouch of Douglas or the vesicouterine pouch, and no macroscopic tumor or disseminated lesions were identified anywhere in the abdominal or pelvic cavity.
No malignant lesion or serous tubal intraepithelial carcinoma, the recognized precursor lesion abbreviated STIC, was identified. Peritoneal washing cytology was negative for malignant cells. Importantly, the authors flag a gap in this workup: p53 and Ki-67 immunohistochemistry of the tubo-ovarian specimens was not performed. Because of this, they conclude that an occult microscopic Müllerian primary cannot be completely excluded, even after radiological, laparoscopic, and pathological evaluation. Primary pleural Müllerian carcinoma, extraovarian primary peritoneal carcinoma, and Müllerian-type high-grade serous carcinoma of undetermined primary origin therefore all remain possible classifications for this tumor.
The discussion places the case in the context of previous reports of thoracic or pleural Müllerian-type serous carcinoma without an evident abdominopelvic primary tumor, which the authors summarize in a table; only a limited number of cases have been reported to date. Most previously reported cases underwent diagnostic laparoscopy or other evaluation of the abdominopelvic cavity, but the authors cite a report by Liapi and colleagues in which serous tubal intraepithelial carcinoma was found in both fallopian tubes, suggesting that microscopic tubal lesions may be relevant to thoracic presentations. The mechanism underlying thoracic-confined Müllerian-type high-grade serous carcinoma remains unclear, and the authors argue that all four candidate explanations, primary pleural Müllerian carcinoma, occult tubo-ovarian disease, extraovarian primary peritoneal carcinoma, and Müllerian-type high-grade serous carcinoma of undetermined primary origin, should be considered when no abdominopelvic primary tumor is detected.
For the patient herself, treatment began with carboplatin plus paclitaxel chemotherapy, initiated seven months after the initial detection of the pleural lesion. The serum CA125 level fell from 178.0 U/mL before treatment to 10.9 U/mL after four cycles, follow-up CT demonstrated shrinkage of the pleural lesions, and the response was assessed as a partial response according to RECIST criteria. No increase in pleural effusion was observed, and her chest and back pain improved. At the latest follow-up she remained under outpatient treatment and was receiving the tenth cycle of chemotherapy. The authors close with a caution that doubles as practical guidance: Müllerian-type high-grade serous carcinoma should be considered in the differential diagnosis of pleural tumors in women even when no abdominopelvic primary tumor is identified, comprehensive radiological, laparoscopic, and pathological evaluation is important for determining the most appropriate classification, and in the absence of an identified primary site, classification should remain cautious, with extraovarian primary peritoneal carcinoma regarded as a possible interpretation rather than a definitive diagnosis. Further accumulation of similar cases, they write, is needed to clarify the pathogenesis, classification, and optimal treatment of this rare presentation.
Subject of Research: A rare case of Müllerian-type high-grade serous carcinoma presenting only with pleural lesions and no detectable abdominopelvic primary tumor
Article Title: Müllerian-type high-grade serous carcinoma presenting exclusively with pleural lesions and no detectable abdominopelvic primary tumor: a case report
Article References: Kaneko, Y., Yanagawa, N., Tomoyasu, M., Shigeeda, W., Yoshimura, R., Kanno, H., Iwai, H., Endo, R., Deguchi, H., & Saito, H. (2026). Müllerian-type high-grade serous carcinoma presenting exclusively with pleural lesions and no detectable abdominopelvic primary tumor: a case report. General Thoracic and Cardiovascular Surgery Cases, 5(1), Article 49. https://doi.org/10.1186/s44215-026-00283-0
Image Credits: AI Generated
DOI: 10.1186/s44215-026-00283-0
Keywords: high-grade serous carcinoma, Müllerian carcinoma, pleural tumor, extraovarian primary peritoneal carcinoma, SEE-FIM protocol, serous tubal intraepithelial carcinoma, immunohistochemistry, PAX8, pleural effusion, case report, carboplatin, paclitaxel
News Source: Nathaniel Bowman. (October 28, 2026). Rare Chest-Only High-Grade Serous Carcinoma Reported in 60-Year-Old Woman. Scienmag.
